The higher the prescription, the thicker the overall lens. If you have a strong prescription, you need to select the most suitable lens to make your lens as thinner as possible. 
Click here to check how to pick out the lens index due to prescription.

For Near-Sighted
The lens for near-sighted will be thinner at the center and thicker at the edges. For frame choice, looking for frames that don't draw attention to the rims is necessary. Otherwise, your lens may look thick or clunky.
In an oversized frame, it can create the classic "coke bottle effect" where a thick lens peeks out of the sides of the glasses. However, this can be solved simply by choosing a shorter, narrower, thicker plastic full-frame or hi-index lens (1.74 index).

For Far-Sighted
The lens for far-sighted will be thicker at the center and thinner at the edges which can result in a "bug-eyed effect" where your eyes are magnified and the sides of the face look diminished. 
This can be solved by choosing a shorter, narrower, thicker plastic full-frame or hi-index lens (1.74 index).